This invention relates to a communication system and, in particular, to an apparatus and method for transmitting and receiving a plurality of digital datastreams while maintaining the relative timing between each of the plurality of digital datastreams.
Digital sampling and processing techniques used to represent and analyze the spectral content of an analog signal are widely known. In some instances, it is desirable to sample an analog signal using a variety of sampling rates thereby generating a series of sampled datastreams. Each of the sampled datastreams thus represents the spectral content of a different spectral bandwidth of the analog signal. The series of sampled datastreams are then processed to analyze the total spectral content of the analog signal. In order for the series of sampled datastreams to accurately reflect the spectral content analog signal, it is imperative that the relative timing between each of the sampled datastreams be maintained during processing.
The processing of the sampled datastreams is generally computationally intensive and thus requires substantial computing resources. The need for computing power is increased in situations that require the sampling of analog signals at different locations. In such cases, sufficient computing resources to process the sampled datastreams are required at each sampling location. It is more cost efficient, however, to transmit each of the sampled datastreams from the remote sampling sites to a central processing site for analysis. In this way, the computing resources of the central processing site are leveraged to support the processing requirements of multiple remote sites.
A problem occurs when a series of sampled datastreams collected from a remote site is transmitted to the central site for processing. Because delays exist in transmitting each of the series of sampled datastreams from the remote site to a central processing site, the relative timing between each of the series of sample datastreams is usually altered. If the relative timing of each of the series of the sampled datastreams is not preserved, the resulting spectral analysis of the analog signal will be erroneous. Accordingly, it is desirable to provide a method for transmitting a series of sampled datastreams to a central processing site while still maintaining the relative timing between each of the sampled datastreams.
The present invention is directed at overcoming the shortcomings of the prior art. The present invention is directed to a method for maintaining the relative timing between each of a plurality of sampled datastreams. A plurality of sampled datastreams are generated at a first site by sampling an analog signal at a plurality of sampling rates that are proportional to a master clock rate. Each of the plurality of sampled datastreams are then packetized into a data-packet stream and are transmitted to a second site. At the second site, the data-packet stream is converted back into the plurality of sampled datastreams. The method for maintaining the relative timing between each of the plurality of sampled datastreams at the second site includes the steps of selecting a pulse generated by the master clock having a time-of-day and marking the pulse with a descriptor. The descriptor and the time-of-day of the pulse are then transmitted to the second site. Then, a next sample, that occurs after the pulse, is identified for each of the sampled datastreams. An offset from the pulse to the next sample is then calculated for each of the sampled datastreams. Next, the descriptor, a pointer to the next sample, and the offset for each of the sampled datastreams are transmitted together with the corresponding sampled datastreams to the second site. Using the pointer, the next sample in each of the sampled datastreams is then located. Finally, the relative timing of each of the series of sampled datastreams is fixed based on the next sample, the offset and the time-of-day of the pulse.
Accordingly, a method is provided for transmitting a series of sampled datastreams to a second site while still maintaining the relative timing between each of the sampled datastreams at the second site.
Other objects and features of the present invention will become apparent from the following detailed description, considered in conjunction with the accompanying drawing figures. It is to be understood, however, that the drawings, which are not to scale, are designed solely for the purpose of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.